This invention relates, in general, to optical processing and to improvements in Vander Lugt and joint-transform optical correlators.
This invention improves optical correlators in two ways. The first improvement is the capability of converting a module containing all optical components necessary for optical correlation as a Vander Lugt correlator to a joint-transform correlator, and visa-versa, by the placement or exchange of only one to three simple optical components without disturbing the other components or their alignment and without changing in the electronics involved. The second improvement is the miniaturization of such optical correlators containing this first improvement to provide the users of personal computers (PCs) with Vander Lugt and joint-transform optical processing capabilities.
It will be apparent to those skilled in the art after a study of the drawings and the written description herein that the first improvement may be incorporated in any optical correlator module of any size. However for simplicity, the invention will be described as part of the miniaturization of such optical correlators.
Miniaturized optical correlators are capable of being mounted on plug-in printed circuit boards, or other mounting means, or desk-top PCs, or capable of being mounted on printed circuit boards, or on other mounting means, for optional external equipment connected to the ports of desktop or laptop PCs. Redesigning the computer interface would allow this invention to operate off of other larger computer architectures, such as VME platforms.
In the first related application, paragraph 1) above, there is disclosed and claimed a miniaturized Vander Lugt optical correlator in a module with a folded optical path technique, along with other optical components to provide optical correlation, adapted to be mounted on a standard personal computer printed circuit board, containing all support electronics. This Vander Lugt optical correlator is capable of being plugged inside a PC or on other mounting means to be used with or in a PC. So far as it is known, this Vander Lugt correlator is the first miniaturization of an optical correlator suitable for such purpose.
In the other related invention, paragraph 2) above, there is disclosed and claimed a one or two-stage miniaturized joint-transform optical correlator in a module with a folded optical path technique, along with other optical components to provide optical correlation, adapted to be mounted on a standard personal computer printed circuit board, containing all support electronics. This joint-transform optical correlator is capable of being plugged directly into a PC or on other mounting means usable with a PC.
In many applications for optical correlators, the user has a priori knowledge of the target image to be identified and uses a Vander Lugt correlator with filters containing a suitably processed reference image (often called a "filter") for comparison to the target image. The Vander Lugt correlator is useful where a finite number of reference filters are required for comparison with the target image, but in the case where too many filters are needed or new situations arise, (ie, little a priori knowledge exists), a joint-transform correlator is preferred because it is more flexible. By saving an image of the new object (or situation), and isolating the portion of interest, this type of correlator can be immediately configured for the new application.
This invention, in addition to miniaturizing an optical correlator, enables the user to convert a Vander Lugt optical correlator to a joint-transform optical correlator, or visa versa, with no electronic changes required. Stated another way, the user has the option of operating this invention as a Vander Lugt optical correlator or as a joint-transform optical correlator by the simple replacement or exchange of one to three optical components without disturbing the other optical components or their alignment.